The present invention relates to a biochemical analyzer, and more specifically to a biochemical analyzer for testing blood and an attenuated total reflection prism cell preferably used in this analyzer.
Analysis of biochemical substances such as fluids of living bodies using the infrared spectroscopic method has been discussed in the journal Analytical Chemistry, 61, 1989, pp. 2009-2015. According to the above journal, the glucose concentration in the blood is measured using a general-purpose Fourier transform infrared spectroscopic apparatus in compliance with the attenuated total reflection (ATR) method.
A sample to be measured is introduced into a flow cell which incorporates a cylindrical ATR prism, infrared absorption spectra are measured at room temperature, and the concentration of the glucose component is calculated based on the method of partial least squares.
The above prior art was not satisfactory in regard to correlation of analytical values compared with the colorimetric method using enzymes that is a reference method for glucose analysis, and was not satisfactory in regard to precision of analysis, either. Furthermore, use of the general-purpose Fourier transform infrared spectroscope requires manual operation for pouring samples, washing the ATR prism and effecting the calibration. When employed in general hospitals, therefore, the biochemical analyzer was very clumsy to use.
In the conventional ATR prism used for the biochemical analyzers, in particular, attention has not been given in regard to the adsorption of blood cells and proteins on the surface of the attenuated total reflection prism when the sample consists, for example, of blood. Therefore, the life of the attenuated total reflection prism was short due to the adsorption of blood components. The attenuated total reflection prism is so expensive that a deteriorated one must be used again after polishing it, making the biochemical analyzer very clumsy to use.
The biochemical analysis based on the attenuated total reflection which involves the above-mentioned problems has been described in, for example, Applied Optics, 27, 1988, pp. 5077-5081.
Furthermore, the following examples have been known in which a substance having a high refractive index or a high molecular membrane is interposed between the surface of the ATR prism and the sample.
Japanese Patent Publication No. 55-500589 of translated version in PCT application.
Proteins at Interfaces, Chapter 21, "Adsorption of Fibronectin to Polyurethane Surface: Fourier Transform Infrared Spectroscopic Studies", pp. 324-338.
Proteins at Interfaces, Chapter 23, "Fourier Transformation Infrared Spectroscopic and Attenuated Total Reflectance Studies of Protein Adsorption in Flowing Systems, pp. 362-377.
Applied Spectroscopy, Vol. 35, No. 4, 1981, pp. 353-357.
Journal of Colloid and Interface Science, Vol. 111, No. 2, June, 1986, pp. 343-362.
Journal of Biomedical Materials Research, Vol. 13, 1979, pp. 893-906.
Analytical Letters, 22(9), 1989, pp. 2065-2073.
However, the above conventional examples have a defect in that the membrane becomes thick and spectrum signals detected via the ATR become so weak that satisfactory precision is not obtained.